1. Field of the Invention
The present invention relates to a vibration detecting system of resilient body for detecting vibration of resilient body having multiple vibration mode, and a vibrating contact detection probe used for a form measuring instrument for measuring a minute surface texture of a workpiece in accordance with the same principle as the vibration detecting system.
2. Description of Related Art
Conventionally, a height gauge (one-dimensional measuring instrument), a coordinate measuring machine, a surface texture measuring machine, a small hole measuring machine etc. have been known as measuring instruments for measuring form and dimension etc. of a workpiece. Some of the measuring instruments employ a contact probe, the contact probe detecting contact with the workpiece to sense coordinates value of the workpiece and positional relationship between the workpiece and the measuring instrument.
A so-called vibrating contact probe has been used as one of the contact probes. The vibrating contact probe vibrates a stylus and detects change in vibration of the stylus caused when the stylus touches the workpiece to sense whether the measuring probe has contacted the workpiece or not with high accuracy.
In order to detect contact by vibration, the vibrating contact probe has a stylus having a contact portion to be in contact with a workpiece at a distal end thereof, a vibrator for vibrating the stylus and a detector for detecting the vibrating condition of the stylus. A vibrating element and detecting element using, for instance, piezoelectric element is used as the vibrator and the detector.
According to thus constructed vibrating contact probe, the stylus is initially vibrated by the vibrator and the change in vibration of the stylus caused when the contact portion of the stylus and the workpiece are brought into contact is detected by the detector. Change in detection signal outputted by the detector is observed to recognize the change in vibration of the stylus.
Incidentally, in the vibrating contact probe, in order to vibrate the stylus at a predetermined vibrating condition, the stylus is ordinarily vibrated with a main vibration mode (e.g. primary vibration mode).
However, even when the stylus is vibrated with the main vibration mode, vibration of a multiple vibration mode as well as the main-vibration-mode vibration is generated to the stylus on account of the configuration of the stylus and influence of the mass of the element attached to the stylus.
Accordingly, the action of the multiple-vibration-mode vibration is reflected on the detection signal obtained by the detector in addition to the action of the vibration of the main vibration mode, the action of the multiple-vibration-mode vibration causing noise on the vibration of the main vibration mode to lower S/N ratio thereof. Further, the wider frequency range of the vibration capable of being detected by the detector catches the more noise, thereby further reducing S/N ratio.
A filter having the same transmission characteristics may be used for restraining noise of the detection signal. However, such filter having certain characteristics corresponding to the main vibration mode has complicated structure and is expensive.
On the other hand, in the above-described conventional contact probe, since a lot of minute electrical connections are provided to the vibrator and the detector, the size and configuration of ordinary connector which establishes electric connection through a plug and receptacle cannot be fitted to a minute stylus in order to prevent cross talk which is required in view of performance. Further, changing work of the electric connection each time the stylus is exchanged is in itself difficult, and causes great problems in view of workability and work speed.
On the other hand, the work can be facilitated and speeded up by exchanging the entire probe including the support side of the stylus not only the side of the stylus. However, such arrangement is extremely expensive.